Flavor enhancement of food as a stimulant for food intake in elderly people

It is often speculated that the age related decline in taste and smell performance can add to the decreased food intake among elderly by causing a change in liking of food. Flavor enhancement (by adding a taste and/or an odor to enhance or intensify the flavor of the food) has been suggested to counteract for the diminished taste and smell performance in order to increase liking and subsequently intake among elderly people. However, there is no clear relationship between an impaired taste and smell functioning and flavor enhancement. In addition, the results of studies on the effect of flavor enhancement on intake are inconsistent. In this thesis we investigated the effect of flavor enhancement on liking and/or food intake in elderly people and the relationship between an altered taste and/or smell performance and liking of flavor-enhanced foods. When flavor enhancement is used as an approach to stimulate intake, it is important to know how elderly respond to a daily repeated exposure of a food. We first examined the effect of repeated exposure to fruit drinks with different sweet intensities on intake, pleasantness and boredom in young and non-institutionalized elderly adults. Second, the relationship between an impaired taste and smell performance and the liking and intake of tomato soup enhanced with MSG (0.12%) and celery powder (3 g) was studied. Third, the effect of flavor enhancement on liking and intake has been examined in nursing home elderly people that received MSG (0.3%) and/or flavors (700 mg) sprinkled over the protein component of their hot meal during 16 weeks. As last, to study the effect of a determined optimal preferred amount of MSG on food intake, we added 0.5% MSG (optimal amount) to mashed potatoes and 2% MSG to spinach and ground beef and measured the intake of these foods among institutionalized elderly. The results showed that the elderly experienced no increase in boredom and pleasantness after daily repeated exposure to fruit juices. Elderly with an impaired taste and/or smell functioning did not show an increase in liking and intake of the flavor-enhanced soup. Thus, no relationship was established between an impaired chemosensory performance and flavor enhancement. Flavor enhancement also did not increase liking and energy intake of the hot meal after 16 weeks nor did an optimal preferred amount of MSG increase intake of mashed potatoes, spinach and ground beef. A standardized flavor enhancement of foods did not prove an effective approach to increase food intake in frail elderly people. Therefore we reviewed the literature to obtain a recent picture on the causes of taste and smell loss in the elderly and to examine if the available methods to measure these losses are adequate. Results of the review showed that elderly are a heterogeneous group with various degrees of taste and smell loss and that the applied methods can distinguish the variations. This result implies a more individual, tailored taste and/or flavor enhancement of foods when it is part of a treatment or used in the prevention of undernutrition. We proposed a future strategy for flavor enhancement of foods in which we embedded the results of this review.